The invention relates to devices for evacuating and washing coated microtiter plate wells. More particularly, the invention relates to devices which wash the sidewalls of microtiter plate wells by directing the expression of a current of wash liquid thereupon.
Many homogenous immunoassays employ a separation and wash step in which bound components are separated from unbound components. If the immunoassay is performed in a coated microtiter plate, the separation step entails the evacuation of the liquid phase from each well within the microtiter plate. Since the evacuation may be incomplete, the separation step may be followed by a wash step so as to remove residual unbound components from the solid phase.
A manifold type device for washing coated microtiter plate wells is disclosed by Namba et al., U.S. Pat. No. 4,635,665, incorporated herein by reference. Namba's device includes an array of paired concentric pipes for both aspirating and expressing liquids. Each pair of concentric pipes includes one pipe for aspirating liquid and an other pipe for dispensing liquid. The aspirating pipe is attached to a vacuum manifold; the dispensing pipe is attached to a liquid manifold. The concentric pipes are arrayed so as to be alignable with an array of microtiter plate wells. Namba's device may be employed for simultaneously evacuating liquid from an entire array of microtiter plate wells by immersing the array of concentric pipes within the liquid phase of the array of microtiter wells and then activating the vacuum manifold. Similarly, Namba's device may be employed for simultaneously expressing liquid into the same entire array of microtiter plate wells, by activating the liquid manifold. When liquid is expressed from Namba's device, it is directed toward the bottom of the well.
Since, coated microtiter plate wells may be coated both on the sidewalls and on the bottom, it is desirable to wash both regions as thoroughly as possible. Accordingly, what was sought was a device which could direct the expression of a current of wash liquid onto the sidewalls of coated microtiter plate wells and impart a swirling motion to such current.